Froth flotation of copper sulfide ores with lignin sulfonates



Patented Oct. 18, 1949 FBO'I'H FLOTATION OF COPPER SULFIDE ORES WITH LIGNIN SULFONATES Robert B. Booth. Sprlngdale, and Roy A. Plckenl,

Stamford, Conn., minors to American Cyanamid Company, New York, N. Y., a corporation of Maine No Drawing. Application January 4. 1946, Serial No.'639,164

4 Claims. (01. 209-466) values are mainly in the form of sulfide minerals,

and also to describe ores whose values may be in the form of sulfide minerals associated with values in the form of native metal and oxide or oxidized minerals. For example, copper ores, and particularly these occurring in the Southwestern United States, contain a portion of their values as sulfides, chalcocite, covellite, and chalcopyrite Even more particularly, the

associated with pyrite, molybdenite, native copper, cuprite, bomite, azurite, malachite, and chrysocolla. Likewise, lead sulfide ores frequently contain galena associated with cerrusite and anglesite, while zinc ores contain sphalerite associated with willemite, smithsonite and calamine.

Beneficiation .of metal sulfide ores by froth flotation has come to be commonly accepted as almost a. standardized procedure. The process is carried out in acid, neutral or alkaline circuit in the presence of a frothing agent and a promoter. use as promoters. The most widely accepted in use are the xanthate and dithiophosphoric acids and dithiophosphates types of sulfide promoters which have been found excellent and achieved almost universal acceptance.

However, it must be realized that in most such operations a relatively tremendous amount of feed is handled for a small amount of desirable mineral in the concentrate. Consequently, the amount of valuable mineral left in the tailing is a highly important factor. The more the valuable constituents that can be recovered therefrom is therefore important in reducing the cost per unit of concentrate obtained. This may be, and often is, a more important consideration, within reasonable limits, than is the grade of the flotation concentrate, since, in view of the extremely high tonnage of ore treated, the consistent reduction of even one or two hundredths of one per cent in the metal content of the flotation tailings results in a considerable increase in the total production of valuable mineral.

The difllculty may be illustrated, for example,

in the concentration of copper minerals from a.

typical feed containing other sulfides, gangue and secondary slimes. Using a good commerciallyavailable promoter, it is perfectly feasible to produce copper sulfide concentrates of higher grade than are commercially required. In doing so.

Many materials have been suggested for.

however, the copper content of the tailing becomes excessively high. A practical economic balance therefore favors the production of a lower grade, but commercially acceptable, concentrate with minimum copper content in the tailing.

Unfortunately, even good practice with the better promoters only very rarely reduces the copper content of the tailing to a point as low as is desirable without making too low grade 8. concentrate. This problem has faced the art for many years and many suggested auxiliary reagents for modifying the action of the promoter during flotation have been ofiered without any real success. It is, therefore, the principal object of the present invention to develop a surfacemodifying agent .whlch will enhance both the selective and collecting power of the better prometers.

Surprisingly, the desired results are simply and easily obtained by using as' a surface modifier for the copper sulfide minerals a lignin sulfonate. This type of reagent appears to have a selective surface-modifying action on the copper minerals, the exact nature of which is not wholly understood. When used in the flotation circuit in conjunction with other substantially standardized reagents, the copper content of the tailings may be red 16961 by as much as one-half or more.

The lignin sulfonate may be used in acid form but we prefer to use the alkali metal or alkaline earth metal lignin sulfonates, and these are available in the form of solutions or dry powders which are easily shipped to the point of use, are readily soluble in water, and may be fed without difllculty. The sodium, ammonium, calcium, barium and magnesium salts have been successfuly used.

The lignin sulfonates used in the present invention may be purposely synthesized or commercially-available products may be used. These latter are often highly purified. However, for the purpose of the present invention this is not essential. In many cases the degree of purity appears to be of concern only in regulating the amount to be used. Since the crude products may be used, a source Of supply is readily available in the material recovered in the sulfate process for the manufacture of wood pulp. While the magnesium salt is useful, it is generally found less satisfactory than is the calcium, sodium or ammonium salts. Since the calcium salt is generally more readily obtainable, it is perhaps to be preferred.

The amount of llgnin sulfonate used will obviously vary with the nature of the ore, the degree of purity, the amounts of promoting reagent required, the temperature of the process water, and many other factors. In general, only enough should be used to produce the desired surfacemodifying action. For most operations this will be found to lie between about 0.01 and 0.30 lbs/ton of feed. 7 While as much as 0.50 lbs/ton or more may sometimes be of benefit with particular ores, in general excessive amounts should be avoided in order to insure against the depressing action exercised by excessive amounts on the desired sulfide minerals. The upper limit, then, may be expressed generally as being somewhat less than that amount which depresses values desired to be recovered. It is quite surprising to flnd that this eflective range of small amounts exists in which useful results are obtained yet an excessive amount can be harmful.

Because the action of the beneficiating reagent of the present invention is one of surface modification, it may be used in any one of several ways.

If time and equipment are available for the purpose, a conditioning operation with the surface modifier before carrying out the flotation is usually advantageous. It may even be desirable in many cases to condition the flotation feed with the surface-modifying agent before the promoter is added thereto, for example by adding the lignin sulfonate to the grinding operation or in a preconditioning step in a mechanical agitator. The surface modifier also may be added directly with the promoter. It may be also used by direct addition to the flotation cell Just prior to or during flotation. It may be fed in these operations in dry form, as a paste, or in water solution, the latter being' preferred in most cases in view of the solubility of the lignin suifonates and hence easier feeding, particularly in small amounts.

It is a feature of the present invention that it may be used in several ways. Its primary purpose is to enable the production of concentrates of equal grade to those produced by the practice of the prior art while obtaining these concentrates with higher recovery of the valuable minerals. On the other hand, if so desired because a premium on extremely high grade is available, it may be desirable to use the surface modifier to obtain recoveries approximating those obtained in the prior art but to obtain themn a higher grade concentrate. Whichever of these two procedures is to be followed will be a factor in determining the quantities of reagents used. This istrue both with respect to the promoter and with respect to the surface-modifying agent of this invention.

The present invention will be described in detail in conjunction with the following specific examples which are meant to be illustrative only and not by way of limitation. All parts are by weight unless otherwise noted.

EXAMPLEI A copper ore from the southwestern part of the United States w-as found to assay about 1.13% total copper and about 0.13% oxide copper and to contain pyrite and chalcocite as the chief sulfide and copper-bearing minerals respectively.

In addition covellite, chalcopyrite, malachite, limonite, sphalerite, quartz, sericite, chlorite, ciotite, and carbonate were found. The ore was ground to minus 65 mesh, lime being added dura A copper ore from the northwestern United States was ground, conditioned with 0.05 lb./ton secondary butyl xanthate and 0.036 lb./ton pine oil. and floated for 5 minutes. Similar tests were conducted with 0.05 lb./ton and 0.20 lb./ton of mono calcium lignin sulfonate. The results of the three tests are given in the following table:

Table II' I Concentrate 7 Per Cent 06 inning Lbs/ton Llgnins Reagent Type fi ggh Assay Recov.

No Lignin Sulfonate Used 70. 0. 37 0. 05 Mono Calcium Lignin Sultanate 5. 45 78. 27 0. 34' 0. 20 d0 5. l3 75. 74 0. 325

. EXAMPLE 3 .4 copper ore from the southwestern part of the United States assaying approximately 1.20% Cu and containing pyrite, chalcocite, covellite, chalcopyrite, malachite, sphalerite, iimonite, quartz; sericite, chlorite, biotite and carbonate was ground to about minus 65 mesh, conditioned at 22% solids with 0.064 lb./ton cresylic acid, 0.028 lb./ton of a 1:1 mixture of sodium diethyl and disecondary butyl dithiophosphates, and varying amounts of lignin sulfonates, and then floated in a Fagergren flotation machine. The

results of these tests are summarized in the following table:

Table III I Concentrate, Per Cent Total Cu Lba/mn Lignins Reagent Type 32 3 Assay Recov. Assay No Lignin Sulfonate Used 15. 81 64. 03 0. 44 0.05 Purified Calcium Lignin Sulfonate 10. 00 84.88 0.10 0.20 ....do 14. 82 70.64 0.38 0. 05 Crude Sodium Lignin Sulionatc 14. 14 72. 40 0. 355

v 0.1) .....do 14.29 68.02 0.40

0. 05 Neutral Calcium Lignin Sulionate .L. 13. 92 73. 10 0. 345 0.1) do 11.62 77.83 0.28 0. 05 Basic Calcium Lignin Sulfonate 11.05 81. 47 0. 235

0.05 Acid Magnesium Lignin sulfonate- 15.60 65.83 0.42 0.fl) 0 17.12 60.80 0.49 0. 06 Neutral Sodium Lignin Sultanate" 14. 97 66. 83 0. 42 0.2) .....do 14.97 68.33, 0.40 0.05 Neutral Ammonium Lignin Sullonate 12. 88 75.88 0. 31 0.20 0 11.00 85.13 0.19

EXAMPLE 4 The primary slime portions of a copper ore from the southwestern. United States, obtained by desliming the ore prior to leaching, were treated with 0.32 lbL/ton crude calcium lignin sulfonate', 0.035 1b./ton potassium ethyl xanthate,

0.06 lb./ton pine oil, and 3.9 lb./ton lime and EXAMPLE5 The lignin sulfonates may be used to advantage in the leach precipitation-flotation treatment of copper ores. per whose copper content is present in an appreciable degree in non-sulfide copper minerals was leached with sulfuric acid, partially neutralized, then treated with iron to precipitate cement copper, and floated with normal reagents, i. e., approximately 0.04 lb./ton of a commercial organic flotation reagent and 0.05 1b./ton of pine oil. A good recovery of the copper was obtained. However, when 0.15 lb./ton of calcium lignin sulfonate is added to the pulp Just prior to flotation, the recovery of copper and the grade of the copper concentrate were improved as indicated in the following table:

Table IV Concentrate. Per

Cent Total Cu flmng Per Cent Total Cu Assay Lbs./tcn Lignins Reagent Type Assay Recov.

Calcium Lignin Bullonate A copper ore averaging 0.83% cop:

We claim:

1. In the concentration by froth flotation of copper sulfide minerals from a feed comprising copper and other heavy metal sulfides. the method of reducing the copper sulfide minerals content in the tailing, which comprises forming an aqueous pulp of the ore, subjecting the pulp to flotation in the presence of a promoter selected from the group consisting of the xanthate, dithiophosphoric acids and dithiophosphate types and 0.01-0.5 pound per ton of feed of a surface-moditying agent for the copper sulfide minerals, which agent is selected from the group consisting of the alkali and alkaline-earth metal lignin sulfonates and collecting the resultant froth concentrate.

2. A process according to claim 1 in which 0.01-0.3 pound per ton of feed of the metal lignln sulfonate is used, the amount selected within these REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,130,574 Breerwood Sept. 20, 1938 2,161,010 Breerwood June 6, 1939 2,355,365 Cole Aug. 8, 1944 2,403,481 Clemmer July 9, 1946 2,407,651

Clemmer Sept. 17,1948 

